Objective-C has a special type, "instancetype". Generally, it is a type
that matches the method receiver type. So, if `Foo.foo` method returns
`instancetype`, then `Foo.foo()` would be of type `Foo`, while
`Bar.foo()` would be of type `Bar` (where `Bar` is a subclass of `Foo`).
Surprisingly, `instancetype` can be used not only as a return type, but
also somewhere inside a return type. cinterop wasn't ready for this.
This commit expands implementation of `instancetype` in cinterop to
cover more cases.
^KT-59597 Fixed
Svyatoslav Scherbina